This invention relates to hand trucks of the type having a lower platen and a manually engageable handle spaced above the platen.
A typical hand truck has a frame with wheels mounted at its lower end and a handle located at its upper end. A load supporting platen extends forwardly from the lower end of the frame. In a common hand truck design, the frame is formed of bent and welded metal tubing, and the platen is rigidly fixed to the frame. The frame is typically quite heavy, due to the weight of the metal frame members which provide strength to support the load carried by the platen.
Alternative hand truck constructions as known, which are the result of efforts to reduce the overall weight of the hand truck while preserving normal load capacity. One such construction is illustrated in Stallbaumer U.S. Pat. No. 5,749,588 issued May 12, 1998, which discloses a hand truck with plastic side frames and a fixed-position platen. The side frames are interconnected with each other by means of structural metal cross-members. The side frames are first formed and then assembled together with the remainder of the components making up the overall frame assembly of the hand truck, and the wheel assembly and platen are then secured to the bottom end of the hand truck frame. While this construction reduces the overall weight of the hand truck, it involves disadvantages in the numerous manufacturing steps and sequences involved, and also exhibits a lack of side-to-side stability in operation. Applicant is also aware of a one-piece plastic rotationally molded hand truck, in which a handled body and platen are formed integrally in a single-step blow molding operation. This construction provides a lesser load capacity than is desirable for certain applications, and also has a relatively thick platen area which supports the load. This construction is disadvantageous, in that it is desirable for the platen to be a thin as possible in order to enable the platen to be easily placed below the load.
It is an object of the present invention to provide a hand truck assembly which is relatively light in weight and which does not involve a significant reduction in load-carrying capacity. A further object of the invention is to provide such a hand truck assembly which incorporates a body formed of a lightweight material such as molded plastic and a metal platen, which provides a low profile platen capable of placement below a load in a conventional manner. Yet another object of the invention is to provide such a hand truck assembly in which the platen is capable of being folded when not in use, to reduce the space occupied by the hand truck assembly during shipment and storage. A still further object of the invention is to provide a folding platen arrangement for a hand truck, which incorporates a unique folding and detent arrangement for supporting the platen in its operative lowered position and for retaining the platen in its inoperative raised position. A still further object of the invention is to provide such a hand truck assembly which incorporates ergonomically advantageous features to facilitate ease of operation.
The invention contemplates a hand truck assembly with a number of features which can be incorporated separately or in various combinations or subcombinations. In a particularly preferred construction, the various features are combined together to provide a hand truck assembly which is compact, lightweight and easy to operate, yet which is capable of handling conventional hand truck loads.
In accordance with one aspect of the invention, a hand truck assembly includes a lightweight body, such as a one-piece, blow molded plastic body, and a metal platen located at the lower end of the hand truck body. The hand truck body includes parallel rail sections, which extend between an upper handle section and a lower area.
The hand truck assembly further includes a set of wheels mounted to the lower area of the hand truck body via an axle which extends through a transverse passage defined by the hand truck body. The platen is rotatably mounted to the axle for movement between an operative lowered position and an inoperative raised position. The hand truck body defines a forwardly-facing support surface which extends upwardly from the platen when the platen is in its operative lowered position, and which supports the load when the hand truck is tipped and supported by the wheels during use. The handle section of the hand truck body extends forwardly from the support surface, and includes a handle member and bumper areas located forwardly of the handle member. The bumper areas define a finger space located forwardly of the handle, to prevent the user""s fingers from being contacted by a tall, flat load which engages the bumper areas.
The platen is mounted to the body by a combination folding and detent mechanism, which provides movement of the platen between its operative lowered . position and its inoperative raised position. The platen includes a planar support area, and a pair of mounting ears which extend upwardly from opposite sides of the support area. Each mounting ear is located outwardly of a side wall defined by the lower area of the hand truck body, and is provided with a slot through which the axle extends. A guide arrangement is interposed between each mounting ear and the side wall of the hand truck body lower area, to guide movement of the platen between its operative lowered position and its inoperative raised position. The guide arrangement includes an outwardly biased detent ball mounted to each side wall in combination with a guide slot and opening arrangement formed in each mounting ear. The detent ball cooperates with the guide slot and opening arrangement to selectively maintain the platen in its operative lowered position and its inoperative raised position, and to guide movement of the platen therebetween as the platen is pivoted on the axle.
The platen is mounted to the hand truck body by means of the axle extending through a slot formed in each mounting ear. The axle includes a wheel mounting section located outboard of each mounting ear, and a wheel is rotatably supported by each wheel mounting section of the axle. Each wheel includes a bushing defining a passage through which a wheel mounting section of the axle extends. A retainer is engaged with each end of the axle, and engages one end of the bushing. The bushing has a length greater than the width of the wheel, and the inner end of the bushing engages the outer surface of the mounting ear. In this manner, the wheels and the platen are supported by the axle alone, which in turn is engaged with the hand truck body.
The platen has a low profile but is shaped so as to provide significant strength and to allow for use of a relatively thin material. The primary load bearing area of the platen consists of the planar support area. A channel is formed at each side of the support area, and a lip extends downwardly from the forward end of the support area. Each channel is generally U-shaped, and defines a height which corresponds to the overall height of the lip. The channels extend throughout the depth of the platen, and impart rigidity to the support area and to the overall structure of the platen.